December 17, 2012

ASCB 2012: Let's get physical

It’s the ASCB annual meeting in San Francisco and, on Sunday,
I attended the mini-symposium on Cell Mechanics and Intermediate Filaments.

One of the themes running through the ASCB annual meeting in
San Francisco is the increasing importance of the physical sciences in cell
biology (as illustrated by Saturday night’s keynote address by US Secretary of
Energy and Nobel Prize-winning physicist Steven Chu). Since the major function
of the intermediate filament cytoskeleton is to help cells bear mechanical
stress, it’s no surprise that the physical sciences were well represented in
Sunday’s session.

Indeed, one of the session’s co-chairs, Sarah Köster, is a
physicist who described the use of X-ray microscopy to analyze how the dynamics
of keratin filaments change in cells undergoing mechanical stress. And Andreas
Bausch described how the techniques he’s used to study the physical properties
of actin networks are now being applied to study keratin assembly and
organization. Jessica Tytell, from Gaudenz Danuser’s lab at Harvard Medical
School used more traditional cell biological techniques to examine how vimentin
intermediate filaments contribute to cell migration.

Keratins and vimentin are the main intermediate filaments
found in the cytoplasm, but lamins are a related family of proteins that form
intermediate filaments inside the nucleus. The final two talks of the session
explored how nuclear lamins helps cells respond to mechanical stress. Lamin
mutations cause a diverse set of human diseases, including Emery-Dreifuss
Muscular Dystrophy, progeria and partial lipodystrophy, and Jan Lammerding
discussed how these mutations might differentially affect nuclear mechanics and
therefore result in different diseases with distinct symptoms. And Dennis
Discher – whose lab has previously shown how the stiffness of the extracellular
matrix influences stem cell differentiation – discussed how this process is
modulated by nuclear lamins. These latter studies might not have used the
biophysical techniques employed by Köster and Bausch, but they certainly
demonstrated how the physical properties of cells have wide-ranging affects on
cell behavior.

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